On the Research Front: The NIAAA Intramural Research Program.

Intramural research at the National Institute on Alcohol Abuse and Alcoholism delves into many aspects of biological science relating to alcoholism, from the genetics of alcoholism to the imaging of alcohol-abusing patients' brains. Drawing on the unique resources within the National Institutes of Health, the Intramural Research Program plans to continue its commitment to conducting cutting-edge research.

A cting under a research mandate ERP concentrates on supporting independ nities. On the NIH campus, NIAAA from Congress, the National ent research projects nationwide and intramural scientists interact daily with Institute on Alcohol Abuse and internationally, whereas the IRP, located many internationally known basic and Alcoholism (NIAAA) has on the NIH campus in Bethesda, MD, clinical researchers (there are more than established broad research goals for itself conducts research employing NIAAA's 3,100 doctorallevel intramural scientists, (see box, p. 61). These entail understand own scientists. This article focuses on the including M.D.'s and Ph.D.'s, at NIH) ing the physiological and environmental IRP's contribution to alcoholism research and are surrounded by one of the most causes of alcoholism, elucidating the by reviewing the program's current pro comprehensive concentrations of medical biological mechanisms through which jects, its efforts to train scientists, and the research talent, expertise, laboratories, alcohol affects humans, and developing directions for its future research. and equipment in the world. The compli effective methods for treating the disease cations of alcohol abuse and alcoholism of alcoholism and for preventing alcohol affect most of the organ systems studied abuse. NIAAA's efforts to reach these UNIQUE ADVANTAGES OF

THE INTRAMURAL RESEARCH PROGRAM'S MAIN GOALS
Train new scientists in the field of alcoholrelated research.
Identify the genetic components that predispose people to developing alcohol problems.
Determine the interactions between genetic vulnerability and environmental factors conducive to or protective of individuals at risk of developing alcohol related problems.
Understand the interaction of alcohol with the many other factors playing causa tive roles in the development of alcohol abuse and alcoholism at the molecular, cellular, and whole organism levels.
Describe alcohol's acute and longterm effects on the cellular and molecular levels of the central nervous system and other body systems.
Learn the role of nutrition in alcohol's effects on the health of the alcoholic and of the developing fetus.
Devise more accurate diagnostic techniques and more effective preventions and interventions.
significantly to many health problems. Accordingly, the IRP formally collabo rates with intramural scientists in many of the other Institutes, including the National Cancer Institute and the National Institute of Child Health and Human Development. Basic and clinical researchers within the IRP also collaborate with each other. Consequently, discoveries made in the laboratory can be incorporated rapidly and costeffectively into clinical research proj ects, and hypotheses derived from clinical observations can be tested using basic research paradigms under the more easily controlled conditions of the laboratory.

Training
The future of alcohol research depends on the continuing dedication of talented young researchers. Since its inception, the IRP has been committed to training. Intra mural researchers serve as mentors to young scientists, providing them with access to wellequipped laboratories and the latest research technology.
The IRP provides multiple levels of training programs, ranging from projects for promising high school and undergrad uate college students to programs for advanced postdoctoral fellows. Special efforts have been made to encourage talented students from families of limited means or minority origins, who often are unaware of the potential for a career in alcohol research, to join the program.
Younger students often participate in summer programs or on a parttime basis during the school year under the direction of senior researchers who ensure that the students become meaningfully involved in research. In addition, medical students, as well as postdoctoral, graduate, and under graduate students in other health special ties, receive training designed to encourage a future commitment to the alcohol re search field.

Clinical Staff Fellowships. The Clinical
Staff Fellowship Program provides train ing in clinical and laboratory settings for physicians early in their careers who are interested in the relationship of excessive alcohol consumption to such diverse areas as internal medicine, neurology, pedi atrics, and psychiatry. In the health sci ences area, efforts are made to attract promising young doctorallevel scientists both from the United States and abroad to work with NIAAA scientists on projects of shared interest. Research exchange opportunities also are available for senior scientists outside NIAAA to collaborate with IRP researchers.
International Training Program. The international program trains postdoctoral scientists; promotes collaborations with senior foreign scientists; and successfully facilitates the mutual exchange of ideas, skills, and crosscultural research. Par ticipating researchers range from promis ing junior scientists with less than 3 years of postdoctoral experience to senior scien tists who are internationally recognized. The participation period may range from several months to several years. Currently a total of 37 fellows from 19 countries work in the intramural laboratories under the auspices of this program's visiting arm. Intramural scientists also are en gaged in 11 international collaborative projects with scientists in 8 countries. For example, in one major project located in Finland, researchers are studying alco holism and impulsive behavior among violent offenders.

QUALITY CONTROL OF INTRAMURAL SCIENCE
Unlike the ERPsponsored projects, intra mural projects are not peer reviewed in advance by outside experts but are re viewed carefully and continuously by senior NIAAA intramural investigators. In addition, the NIAAA Board of Scien tific Counselors, which comprises emi nent senior scientists from outside NIH, comprehensively reviews each laborato ry's ongoing research at least once every 4 years. The Board critically evaluates each intramural laboratory's current research, offers suggestions for improving research, makes recommendations on the promotion and tenure of individual scien tists, and proposes promising areas for expanded research efforts. Reports con taining these evaluations, and the actions taken in response to them, are then sum marized for the NIH Board of Scientific Directors, who direct the intramural pro grams of all the NIH Institutes and for the NIAAA National Advisory Council, which oversees the quality of NIAAA's overall program.
Because of the retrospective review process, the IRP can change its research priorities more expeditiously than can most participants in the prospectively reviewed ERP. Thus, the IRP has the unique flexibility to pursue promising new avenues of inquiry. In addition, intramural research funding and other resources are generally stable over rela tively long periods of time, whereas extramural grants must be applied for at regular intervals. Stable funding enables the IRP to conduct longterm research projects that may have uncertain out comes, capitalizing on the equipment and expertise available at NIH.

Laboratory of Membrane Biochemistry and Biophysics
Norman Salem, Ph.D.

Division of Intramural Clinical and Biological Research
Markku Linnoila, M.D., Ph.D.

Laboratory of Molecular and Cellular Neurobiology
Forrest Weight, M.D.

BASIC RESEARCH IN THE IRP
The genetic and nongenetic research conducted in the IRP share several com mon themes. These include the molecular theme of identifying alterations in sero tonin 1 function in brain cells of individu als at risk for alcoholism; the clinical theme of classifying subtypes of alcoholic individuals by characteristics such as age at disease onset and associated psychiatric and behavioral problems; and the neuro physiological theme of focusing on trait differences, including inherited variations in people's electroencephalograms (EEG's) and differences in their neuroen docrine and behavioral responses made in the laboratory under the influence of specific pharmacological agents. Each theme is discussed below.

Genetic Research
Researchers have long known that people who have parents or other close relatives with alcohol problems are more likely to develop similar problems than are those who do not have this family history, thereby implicating a genetic element in alcoholism. ments for particular groups of alcoholics based on an understanding of the various biological and environmental factors con tributing to their alcohol problems. The increased risk of developing alcohol problems that are associated with being the child of an alcoholic does not mean that this outcome is inevitable. Both genetic and environmental factors un doubtedly influence whether alcohol problems develop. For example, people who have inherited either impulsive or anxious temperaments are more likely to become alcoholic, but only a minority do. Identifying genetic vulnerability factors helps to reveal the impact of environ mental influences, which interact with the genetic factors in complex ways. What ever the ultimate nature of the genetic factors involved in alcoholism, they al most certainly are complex, involve multiple genes, and interact with early developmental experiences as well as current life stresses. A significant part of the IRP's genetic research effort focuses on characterizing these factors and the relationships between them.
Population Studies. The IRP projects aimed at solving the puzzles presented by the genetics of alcoholism cover a range of topics. Researchers in the Laboratory of Neurogenetics (LN) are studying alco holism in particularly highrisk, homoge neous groups, including large American Indian families. Because alcoholism is highly prevalent in many American Indian communities, it is particularly important for researchers to define the role of genetic vulnerability factors and such interacting environmental factors as employment, income, acculturation, and education in these populations. In studies on American Indians and other groups that are genetical ly, socially, and clinically more homoge neous than the general population, re searchers also seek to isolate genetic elements that can be associated more widely with the general population's vul nerability to alcohol problems.

Molecular Studies.
In another project, LN scientists are directly examining gene struc ture, revealing differences in the makeup of key proteins involved in signal transmission among nerve cells. For example, LN scien tists have found variations of several of the proteins involved in the function of the neurotransmitter serotonin among subjects and are now investigating these variations for their possible involvement in vulnerabil ity to alcoholism (figure 2).
LN scientists also are investigating the control of the expression of genes that are involved in the function of neurotransmit ters. This research is important because alcohol itself, withdrawal from alcohol, and other stressors can alter gene expres sion and actually change the way the brain works. For example, serotonin ordinarily inhibits a variety of behaviors, including aggression, food consumption, and probably alcohol consumption. How ever, certain stresses can reverse this inhibition. LN scientists recently have identified regulatory elements at the gene for tryptophan hydroxylase, a critical enzyme involved in serotonin synthesis. Activation of these elements-by, for example, glycocorticoid stress hormonesproduces profound changes in the expres sion of tryptophan hydroxylase, which in turn alters serotonin synthesis. Differ ences in serotonin levels predispose some people to more impulsive behaviors, including alcoholism. Therefore, scien tists must identify the genetic variants that determine differences in the genes in volved in the function of this neurotrans mitter as well as determine the molecular mechanisms by which environmental factors can exert an influence, such as changing serotonin's rate of synthesis.

Molecular and Cellular Research
Much of the IRP's basic research focuses on understanding alcohol's effects on the body at the most basic cellular and molec ular levels. Research includes work by the Laboratory of Molecular and Cellular Neurobiology (LMCN) in determining alcohol's effects on certain neurotransmit ters, such as serotonin (discussed above), and their receptors, which are fundamen tal to the various communications occur ring within and between brain cells and which alcohol appears to disrupt. Other research conducted by the Laboratory of Membrane Biochemistry and Biophysics (LMBB) includes studies of cell mem brane structure and function and how alcohol affects essential membrane struc tural components called fatty acids.

Alcohol's Effects on Neurotransmitter
Systems. Receptors are proteins in the cell membrane that react to specific neuro transmitters normally present in the brain, such as serotonin. However, receptors also respond to the disruptive effects of alcohol and other drugs. LMCN scientists were the first to discover that alcohol spe cifically affects a receptor for the neuro transmitter glutamate, the NMDA receptor (named for NmethylDaspartate), which is known to be involved in cognitive activity and motor coordination.
When binding to the NMDA receptor, glutamate activates a system permitting calcium to enter the nerve cell, which in turn triggers other cellular processes that excite the nerve cell and produce nerve impulses.
The LMCN studies showed that alco hol's effect on the receptor, which inhibits the nerve cell from sending impulses, depends on concentrations in the range of intoxicating levels, making it a likely candidate for involvement in the behav ioral effects of intoxication. Because the NMDA receptor also is known to be involved in learning, early fetal develop ment, and susceptibility to seizures, such a common mechanism could well explain alcohol's diverse effects on memory and fetal development and possibly could explain physical dependence and symp toms such as seizures that often result from alcohol withdrawal.
It is important to recognize that the many transmitter systems in the brain, such as the NMDA/glutamate system, do not act in isolation. Alcohol's actions on one system may trigger events in other regula tory systems or change the sensitivity of those systems to their normal stimuli.
Current work by LMCN scientists on the NMDA receptor and several other neurotransmitter receptors is in the van guard of basic alcohol research. Although most of this work has concentrated on immediate alcohol effects, studies of the longterm effects of alcohol on neuro receptor systems also are in progress. Such effects include changes in receptor gene regulation and expression (discussed above), changes in the structure of recep tors, and modified nerve cell development in fetal alcohol syndrome (FAS). LMCN's work also includes research on the molec ular and cellular basis of other behavioral effects of alcoholism, such as tolerance (the requirement, over time, for increased amounts of alcohol to produce the same effect) and craving.

Alcohol's Effects on Cell Membranes.
In other studies of molecular and cellular biology, LMBB has made major advances in understanding alcohol's effects on fatty acids in cell membranes. These fatty acids are found in the form of complex phospho lipids and play an essential role in the func tion of cell membranes. Chronic alcohol consumption leads to a decrease in the levels of essential fatty acids in various organs, including the brain. In addition, an inadequate supply of fatty acids during fetal development (if the mother's diet is defi cient) and during postnatal early develop ment leads to a deficit in cognitive and visual functions. These deficits may occur because repeated alcohol intake, combined with an inadequate diet, prevents the accu mulation of fatty acids in the fetus's brain. Researchers believe that the alcohol induced decline (or insufficient buildup in fetuses) of particular fatty acids in the nervous system underlies some of the patho logical effects of alcohol abuse on the brain.
Taking this research one step further to investigate how alcohol causes fatty acid levels to decline, recent studies have suggested that alcohol can alter the metabolism of these membrane lipids so that they are degraded faster by the body's natural processes. It appears that the brain or liver or both attempt to com pensate for this increased rate of degrada tion by increasing the rate at which essential fatty acids are synthesized. However, when the alcohol dose is too high or repeated too often (as it is in alcoholism), the system cannot compen sate, and the level of essential fatty acids may become inadequate for the cells to function properly. A poor diet (i.e., one that has low levels of essential fatty acids and antioxidant vitamins and minerals) may exacerbate this effect. Many alco holics obtain much of their caloric intake The structure of a serotonin receptor subtype (a protein that binds the neurotransmitter serotonin in the nervous system). Two amino acid substitutions (amino acids are the building blocks of proteins) have been found to occur in rare instances in this subtype. The substitutions are the result of differences in the genes that encode the protein. In the first, Glycine (G) is substituted for Serine (S). In the second, Isoleucine (I) is substituted for Valine (V). Studies of these receptor differences, which exist in some people but not everyone, could lead to the identification of differences in receptor function that influence alcohol preference and impulsive behavior. In 1966 the prevailing view of alco holism as a breach of morality began to give way to the perception of the disor der as an addiction, a condition at least partially beyond the control of its sufferers. The public and, more impor tantly, physicians and scientists began to accept that alcoholism might be a medical problem, a disease brought on by complex factors that works insidi ously to destroy a range of body func tions, from liver and pancreatic activity to mental processes, such as memory.
Prior to this period, the Federal Government had provided little funding to support alcoholism research. In October 1966, however, the National Institute of Mental Health (NIMH), directed by Stanley F. Yolles, M.D., established the National Center for the Prevention and Control of Alcoholism. The new Center, which was located with NIMH at St. Elizabeths Hospital in Washington, DC, was intended to support research endeavors and efforts to train scientists in the alcoholism field. It also was responsible for com municating research findings to educate the public and to better inform people in the treatment and service arenas of the field. Yolles recruited Jack H. Mendelson, M.D., an alcoholism re searcher at Harvard University, as the Center's first director (Mello and Mendel son 1971).

Setting Up: The First Years
Before he would agree to direct the Center, Mendelson insisted that in addition to promoting extramural research (by provid ing grants to applicants from private in stitutions wishing to study aspects of alcoholism), the Center initiate an Intra mural Research Program (IRP) to be run by Center scientists at laboratory facilities at St. Elizabeths. NIMH agreed to support intramural research, and Nancy K. Mello, Ph.D., also from Harvard University, was appointed as the IRP director.
Both Mendelson and Mello first be came committed to understanding alco holism and its causes while receiving their medical and scientific training in Boston, MA. According to Mendelson, at that time both researchers "were impressed with [the prevalence of] a number of biomedi cal problems" among patients at the city's hospitals. "One of the major ones was alcohol abuse and dependence," he said.
The two researchers believed that alcoholism should be an area of mutual interest for scientists trained in a range of fields, such as cardiology and molecular biology as well as psychology. According to Mendelson, they believed an intramural program could "maintain continuity for multidisciplinary investigative work," allowing longterm, crossdisciplinary studies to be conducted without interrup tion. The program also could "provide a very important resource with respect to training individuals from various disci plines" to do alcoholism research.
With the goal of attracting scientists and postdoctoral research fellows with a variety of backgrounds, the Center began recruiting. The directors found that despite the widespread stigma still attached to alcoholism, scientists wanted to carry out research in this field. As a result of these efforts, research projects progressed over the next several years at St. Elizabeths in areas such as clinical investigations of pharmacological treatments for alcohol craving and withdrawal syndrome; genetic predisposition to alcoholism; alcohol metabolism; alcohol's effects on the brain; and the design and breeding of animal models of alcohol dependence, including some of the first models of alcoholism in other primates (i.e., rhesus monkeys).
According to Mendelson, the IRP was, and still is, unique in its ability to "bring persons together to work in concert" who possess different fields of knowledge and varying ideas about how alcohol may effect disease, encouraging people to "share their ideas and interact" to achieve results that "hopefully transcend what their own special interests are."

Gaining Acceptance: 1978-82
Research continued in both the extramural and intramural programs after the Center became the National Institute on Alcohol Abuse and Alcoholism (NIAAA) in 1971 (see the article by Hewitt, pp. 12-16). A handful of researchers affiliated with the IRP, however, believed that it would not be recognized as a center of leadingedge research until it could be located with other biomedical intramural programs on the campus of the National Institutes of Health (NIH) in Bethesda, MD. The old stigma dismissing alcoholism as a mental problem that plagued only social deviants still echoed through the research commu nity, making it difficult for alcoholism researchers to have their work acknowl edged as a contribution to medicine.
In 1977 NIAAA asked Gian C. Salmoiraghi, M.D., Ph.D., a former direc tor of NIMH's Division of Special Mental Health Research, of the Clinical Neuro pharmacology Research Center, and of research at St. Elizabeths Hospital, to become the IRP's acting director. Salmoir aghi believed that the program "needed to acquire legitimacy for the field" by being accepted as a part of the larger intramural research community at NIH. He met with NIH's director of intramural research, DeWitt Stetten, M.D., to press his case. By pointing out to Stetten that, according to national statistics, 10 percent of the pa tients admitted to NIH's clinical wards had alcohol problems that should be understood and addressed, Salmoiraghi "achieved tolerance at NIH." The IRP was promised space for housing patients and conducting clinical research in NIH's clinical building on the Bethesda campus.
During his tenure as acting IRP director, Salmoiraghi recruited Markku Linnoila, M.D., Ph.D., who now directs the IRP, as chief of the newly created clinical labora tory at NIH. Moving the IRP to NIH would allow collaborations to develop, not only between scientists of various disciplines but between intramural programs as well. The extensive facilities and other opportu nities the IRP found at NIH eventually would allow the program to broaden its research focus and grow to become the multidisciplinary center envisioned by its former directors.

Expansion: 1984-90
When Boris Tabakoff, Ph.D., took over as director of the IRP in 1984, its clinical laboratory still was being organized on the NIH campus, and according to Tabakoff, the program was drawing from its new location "tremendous leverage" to become like the other highly diversified IRP's at NIH. For example, unlike private hospitals, which are hampered by costs, the clinical laboratory could house 10 patients on its ward for at least 40 to 50 days, allowing physicians to observe phenomena that appear over time, such as the effects of detoxification and with drawal on memory.
Also, NIAAA researchers could gain access to new technologies, such as costly imaging equipment, by sharing the expense with other NIH IRP's and recruiting imag ing experts who merged their knowledge with that of the alcoholism researchers to develop new insights and novel techniques for use in future studies. Thus, the IRP pioneered research in certain fields, as it has in its ongoing use of magnetic reso nance imaging (MRI) to study alcohol's damaging effects on brain function.
Because of the quality of its research and its leadingedge direction, the pro gram continued to gain acceptance in the NIH community during the mid1980's. During his tenure as the IRP director, Tabakoff also was invited to represent NIAAA on NIH's decisionmaking body, the Board of Scientific Directors, some thing NIAAA had been excluded from when he arrived. This accomplishment symbolizes what Tabakoff regarded as the "complete turnaround" in NIH's attitude toward research on alcoholism that had taken place since the IRP's founding at St. Elizabeths Hospital.
As the IRP received more space and respect at NIH, it expanded its research efforts in areas such as genetics; molecular biology (i.e., the study of the alcohol molecule's effects on the human body's chemistry); immunology, including alcohol and AIDS; imaging; and the efficacy of new medications in treating aspects of alcoholism. It also undertook research collaborations with other IRP's, such as those of the National Cancer Institute and the National Institute of Diabetes and Digestive and Kidney Diseases. The train ing program for physicians and Ph.D. researchers also continued to expand and diversify, enlisting specialists from in ternists and psychiatrists to molecular geneticists to conduct clinical and basic research while learning about the alco holism field (Tabakoff and Petersen 1988). The IRP's access to NIH facili ties and its unique regimen of research projects attracted many of these trainees.
Tabakoff noted that under his direc tion, the IRP made initial contributions to alcohol research in areas such as neurology and immunology that later were carried on by private institutions through the extramural program. Such interplay allowed the two programs to complement, rather than compete with, each other.
Like his predecessors, Tabakoff emphasized certain unique aspects of the IRP in speaking about its value to the field of alcoholism research. One aspect is the program's flexibility. "Researchers," he said, "do not need to achieve results within a specified length of time, allowing for the pursuit of projects that have a long period before payoff." But the same flexibility allows IRP scientists to shift their priorities to take advantage of "windows of opportu nity" for new research. Two such pro jects began when the need to study relationships between alcohol and AIDS became apparent and when the value of MRI in studying brain function was demonstrated.
From its inception, NIAAA's IRP has been intended to conduct leading edge projects in many areas of biomedi cal and psychological research. The IRP has helped to tear down barriers, such as the stigma surrounding alco holism; has reached its goal of becom ing a multidisciplinary program; and, according to Mendelson, has "main tained throughout the years a tradition of excellence."

Alcohol's Actions on Membrane
Components. Another example of basic research conducted on the molecular level involves alcohol's direct effects on the molecules composing the cell membrane. LMBB researchers have shown that alco hol interacts with membrane lipids at the cell's surface in much the same way that water does. Under normal conditions, water covers the entire membrane surface, including the lipids, proteins, and carbo hydrates. The layer of water around these molecules is important for maintaining their conformations (i.e., their size and structure) and functions, and it is very likely that the replacement of water by alcohol in this layer alters these functions.
Researchers also have found that although alcohol acts on the membrane surface, the results of the interaction affect the membrane's interior. Changes caused by alcohol at both the surface and interior of the cell membrane can alter the cell's function. To study alcohol's influ ence on the membrane's interior, LMBB has modeled the outside of the cell where alcohol acts with an artificial membrane using the lipid components most com monly found in the outer membrane leaflet. For the first time, researchers have detailed the effect of each of these com ponents on the way in which alcohol alters membrane structure at all depths across the membrane, including the interi or. These studies are important in under standing how alcohol affects membranes in living cells.
One example of this type of research in LMBB is the first direct observation that alcohol's ability to change membrane receptor function can depend on its effects

Meta II (active form) Rhodopsin (inhibited form)
The structure of the protein rhodopsin, a typical G protein-coupled receptor, and its activated form, metarhodopsin II (Meta II), located in a cell membrane. The Meta II form is created when a molecule at its center, called retinal, changes its conformation in response to absorbing light. When retinal changes, the receptor increases in volume. Alcohol increases the amount of active receptor (i.e., Meta II) formed by loosening the packing of the phospholipid fatty acids in the membrane surrounding rhodopsin and allowing it to expand into its Meta II conformation. Neuronal and retinal tissues are rich in the specific phospholipid fatty acids that respond to alcohol's presence, which suggests that the phospholipids may play a role in modifying receptor activity in response to acute alcohol exposure.  on the lipid content of the membrane surrounding the receptor. Scientists exam ined alcohol's effect on the function of the visual receptor, rhodopsin, in cell membranes taken from the retina of the eye. Different from the receptors previous ly described, this G proteincoupled recep tor system is responsible for lowlight level vision. When rhodopsin absorbs light, it activates a G protein in the cell's interior by increasing in volume to assume its activated form, called metarhodopsin II (or Meta II). Researchers found that alcohol loosens the packed phospholipid fatty acids (i.e., the portion of the lipids that makes up the membrane's interior) around a rhodopsin molecule, enhancing the recep tor's ability to expand into its Meta II conformation (figure 3). When researchers replaced the lipids in their model mem branes with polyunsaturated fatty acids, alcohol's effect on phospholipid packing was even more pronounced. The increased formation of Meta II produced by shortterm alcohol exposure probably results in the hyperactivity of this signaling pathway. In contrast to this finding, the previously described loss of polyunsaturated fatty acid components of membrane phospholipids caused by longterm exposure to alcohol may dimin ish alcohol's effect on this pathway. Hence, the loss of polyunsaturated fatty acids may contribute to alcohol tolerance developed during chronic alcohol use. These findings also agree with the ob served impairment of certain visual func tions previously described as related to a deficiency in essential fatty acids during fetal development.

Alcohol's Effects on Fetal Development.
The fetal effects of heavy maternal alco hol use also are well known, but again, their cellular and molecular bases are not. LMBB is developing a new animal model of FAS to enable further study of the damage alcohol inflicts during fetal devel opment. The model is based on the theory (discussed above) that alcohol prevents fatty acids from accumulating in the brain, thereby contributing to develop mental difficulties. The combination of a diet limited in polyunsaturated fats (of which fish is a good source) together with daily alcohol exposure during pregnancy may enhance alcohol's negative effect on fatty acid buildup. Scientists are investi gating the combination of alcohol and this type of diet in animals as an appropriate model of those alcoholics, including some pregnant women, who experience periods of poor nutrition. Thus, the offspring of animals maintained on this diet and given alcohol may reflect more accurately the molecular characteristics of a person with alcoholrelated birth defects than have past models.
Other laboratory studies conducted within LMCN use in vitro (i.e., simple controlled cell cultures) or in vivo (i.e., slices of rat brain) models to study the molecular basis of alcohol's neurotoxicity and its effects on the formation of connec tions between cells in the developing brain. These studies will show how alco hol disrupts the development of brain cells and the communication paths be tween cells and also will help explain the physiological damage seen in FAS.

Animal Model Development.
One great difficulty encountered in research-even with the newer neuroimaging techniques, such as positron emission tomography (PET) and magnetic resonance imaging (MRI), that are now available for studying the intact human brainhas been the investigation of alcohol's action at molecular and cellular levels. Therefore, an important aspect of intra mural research has involved developing appropriate animal models for use in many areas in addition to the develop mental studies mentioned above. These include using nonhuman primates to elucidate the molecular, genetic, develop mental, and environmental variables contributing to individual differences in alcohol preference, sensitivity, and con sumption levels.

CLINICAL STUDIES
Although basic research on the underlying mechanisms involved in alcohol abuse and alcoholism is crucial to devising rational prevention and treatment strategies, these clinical goals also must be pursued direct ly. The IRP's clinical research efforts are directed toward defining more accurately alcohol's adverse health consequences, making diagnostic techniques more precise and less dependent on patients' own de scriptions of their drinking behavior, and devising improved interventions. Ulti mately, alcohol abuse and alcoholism are human problems that must be faced in the very real world of the family, the school, the workplace, and the clinic.
Although most animals can be induced to consume alcohol, they typically do not abuse it in the same way that people do, GLOSSARY Alcohol abuse: Refers to patterns of problem drinking that have resulted in detrimental effects on a person's health and/or social interactions.
Alcohol dependence: Also known as alcoholism. Refers to a disease characterized by abnormal alcohol seeking behavior that leads to impaired control over drinking.
Antioxidant: A substance that inhibits chemical oxidation (a chemical reaction that usually involves loss of hydrogen from a molecule), such as vitamin E.

Electroencephalogram (EEG):
A recording of electrical activity that emanates spontaneously from nerve cells in the brain. Variations in the patterns of an EEG correlate well with activity and conditions in the brain. Thus, EEG's often are used as diagnostic tools.
Fatty acids: Molecules that constitute components of fats (i.e., lipids). Fatty acids are essential components of the phospholipids in cell mem branes. Saturated fatty acids differ structurally from polyunsaturated ones in the numbers of double bonds that exist between the carbon atoms that make up their chains. Saturated fatty acids have no double bonds and are less likely to unite with other compounds. Polyun saturated fatty acids usually have between three and six double bonds and are more reactive.

G proteins:
Molecules within cells that act as messengers, linking protein receptors in the membrane to molecules that perform specific functions inside the cells (e.g., en zymes, which are proteins that accel erate specific chemical reactions).
Gene: A sequence of nucleotides (i.e., the basic molecular units of de oxyribonucleic acid [DNA]) that, when translated by mechanisms in a cell, encode a protein.

Gene regulation:
The process of modifying the rate at which a gene is expressed as a protein. Sequences of DNA that are called regulatory elements influence gene expression.
Neuroendocrine: Refers to interactions between the nervous and endocrine systems of the body. For example, nerve cell activity often is influenced by hormones secreted by endocrine glands, such as the pituitary.
Neurotransmitters: Members of a group of substances in the nervous system that are responsible for transferring a nerve impulse from one nerve cell (i.e., neuron) to the next. These chemicals are released by one neuron and travel to a target neuron. At the target neuron's sur face, they attach, or bind, to specific receptors to produce an impulse in the target neuron.
Neurotransmitter receptors: Proteins located on the outer surface of neurons that attach, or bind, specific neurotransmitters to become acti vated and either initiate or inhibit nerve impulses. These receptors (e.g., the NMDA receptor) often are named for synthesized compounds that they bind in addition to natural ly occurring neurotransmitters. For example, the NMDA receptor is named for NmethylDaspartate, a synthetic compound that has been found to bind and activate the re ceptor in the same way that the naturally occuring neurotransmitter glutamate does.
Phospholipids: A type of lipid, or fat, found in all cells that forms the structural basis of cell membranes.
Polymorphism: The occurrence of two or more different forms of the same genetic trait in a population. For example, in a population of rats that otherwise are genetically iden tical, one group is sensitive to the effects of alcohol, whereas the other group is much less sensitive. Sensitivity to alcohol's effects is polymorphic in this rat population.
Regulatory elements: DNA sequences located near a gene. These influence protein production from the gene by helping to define the rate at which the gene is expressed.

Serotonin:
One of the primary neuro transmitters in the central nervous system that excites target neurons.
which limits their usefulness as models of alcoholism. Moreover, animals are not affected by the cultural, social, intrapsy chic, and interpersonal forces that play roles in alcohol use by humans. Psycho social and biological differences between humans and animals make human and animal research complementary; neither can adequately replace the other. Clinical studies currently underway at the IRP are designed to explore many aspects of alcoholism that parallel those being studied in the basic research labora tories-from alcoholism's genetic deter minants and biological origins, and its impact on neuroanatomy and cognitive functioning, to improved intervention methods. Investigators are pursuing clini cal research on these aspects of alcoholism in populations ranging from alcoholic patients and their families living in the Washington, DC, area and American Indians on reservations in the Southwest to violenceprone male alcoholics living in Finland (mentioned above).

Clinical Consideration of Genetics
Investigations of the genetic and biological bases for alcoholism involve examining families in which alcoholism is present. By studying families with an alcoholic mem ber, researchers can look for shared causal factors, ranging from the family's dynam ics to members having similar genetic and neurophysiological characteristics. Study ing biological similarities between alco holic patients and their children may reveal characteristics that could lead to the early detection of children at risk for abusing alcohol. Intramural research in this area potentially can identify biological indica tors, or "markers," of vulnerability to alcohol abuse. The indicators (i.e., observ able characteristics) are known as markers if they reliably are found to be inherited along with a tendency to develop alco holism. Such markers eventually may be useful in detecting vulnerability to alco hol's effects even before a person takes his or her first drink.
One example of a potential biological marker for alcoholism is the work done by the Laboratory of Clinical Studies (LCS) on examining characteristic pat terns of the brain's electrical activity (referred to as EEG activity). The distinct patterns found in certain individuals may be useful as markers of susceptibility to alcohol problems. In addition, the ways in which the EEG patterns are transmitted genetically within families could provide

Figure 4
An axial slice (i.e., an image taken along a horizontal plane) from a magnetic resonance imaginggenerated picture of the brain. In the lower image, the same slice is shown as a compilation taken from positron emission tomography (PET) scans of 19 detoxified alcoholics and 10 nonalcoholic volunteer males. The PET image shows differences between the alcoholics and the volunteers in the brain's glucose metabolism. The dark blue regions are areas in which the alcoholics exhibited significantly lower glucose use than the volunteers.
clues to the ways in which alcoholism itself is inherited.

Physiological Aspects of Clinical Research
Metabolism and Nutrition. One example of the shared interests of basic and clini cal research focuses again on alcohol's interaction with fatty acids. IRP re searchers in LMBB are studying the synthesis and breakdown of essential fatty acids by the liver in both adults and in fants. The researchers are using a highly sensitive and specific, noninvasive tech nique, developed in LMBB, that measures the liver's metabolic activity with respect to converting dietary fatty acids to the more saturated forms required by the brain and other organs. This study may help scientists understand the mechanism that underlies the loss of essential fatty acids in alcoholics.
In related research, scientists studied premature and term infants to determine the stage of maturity at which the liver is capable of forming the essential fatty acids required for optimal brain develop ment. A surprising result of this study was that even quite premature infants had the capacity to convert these fatty acids in the liver within 1 week after birth. Basic studies such as this are crucial for devel oping an understanding of the pathways by which the nervous system accumulates the specific polyunsaturated fatty acids that it requires and the disruption of this process during fetal alcohol exposure. Furthermore, this study has potentially important implications for the formulation of infant formulas that optimally support neural development.
Imaging. Advanced brain imaging tech niques-PET and MRI-increasingly have served as important noninvasive tools for studying the living human brain. These techniques permit researchers to detect more accurately neuroanatomical changes correlated with chronic alcohol use and functional changes in brain tis sue, such as rates of glucose metabolism, which is the body's major energy source. LCS researchers compare images of a person over time or of alcoholics with nonalcoholics and quantify regional changes or differences in the brain (fig  ure 4).
Scientists have criticized imaging studies, however, for their lack of an ac ceptable means of determining the signifi cance, in statistical terms, of differences in brain images obtained by MRI and PET scanning. Recently LCS researchers have made progress in this area using sophisti cated statistical techniques for analyzing these complex images. Because determin ing whether differences between brain images are significant is such a basic problem with this otherwise useful tool, LCS also is pursuing alternative ways of determining these differences.
Using the recently developed statisti cal techniques, researchers have found correlations among regional brain glucose metabolism and age, severity of alco holism, and cognitive ability. Brain glu cose metabolism tends to decrease (i.e., is negatively correlated) with advancing age in alcoholics but not in nonalcoholics. PET scans of patients who show loss of control and are physically violent also have shown significant decreases in the patients' ability to metabolize glucose in certain brain areas. Such patients also experience a greater frequency of panic attacks, alcohol abuse, and alcoholism than do healthy volunteers.
Researchers have used another imag ing medium-MRI-since early 1994 to study olfactory stimulation's effects on regional brain blood flow. The goal of this research is to understand the func tional neuroanatomy of brain areas associ ated with the desire for food or alcohol. Thus far, researchers have found that pleasant odors produce a significant increase in blood flow in specific brain areas-the nucleus accumbens, which includes an olfactory center, and the amygdala and hypothalamus, both of which are involved in behavioral func tioning. This research may help scientists devise better ways of reducing drinking relapses in alcoholics undergoing treat ment by investigating alcoholics' brain responses to alcoholic beverages.
Intramural neuroimaging research also has emphasized the use of neuroimaging methods that can provide detailed three dimensional views of the living human brain. Such views enable scientists to visualize and measure more accurately neuroanatomical and functional changes associated with heavy alcohol use.

PharmacologicalChallenge Research.
Among the most serious effects of chronic heavy drinking are those on thinking, problemsolving, and memory. Unlike nonalcoholic volunteers, the aging, or neuropsychiatrically impaired groups, alcoholics show selective impairments in those cognitive functions involved in monitoring mental operations under vol untary control. Drug challenges (i.e., the acute administration to nonalcoholics of drugs other than alcohol that mimic some of alcohol's effects) are useful in delineat ing the types of impairment that are pre sent in alcoholics and others. Because the actions of the drugs being given to sub jects are well defined, researchers can clarify alcohol's effects by determining whether it produces the same reactions in the subjects as the other drugs produce. For example, acute doses of benzodi azepine tranquilizers such as diazepam mimic some of alcohol's effects on cogni tion, such as a reduced ability to judge one's own accuracy of memory recall and of identifying sources of the information that is remembered. These druginduced deficiencies also resemble those produced by certain anesthetics such as ketamine. Ketamine is a known blocker (i.e., antag onist) of the receptor believed to be in volved in longterm memory consolidation. Certain drugs-benzodiazepines and alcohol-administered to normal subjects also produce changes in how they, as well as how alcoholics, retrieve information. Thus, these drugs may act on the same brain receptor as ketamine.
The effects of these drugs on certain aspects of memory may be important in understanding patterns of uncontrolled drinking, alcohol's reinforcing or reward ing effects, and the reduced ability of alcoholics to recognize various stimuli. The IRP is now extending this research to study alcohol craving and cognitive func tions in children at risk for developing alcoholrelated problems.
Other pharmacologicalchallenge re search is helping to clarify the distinction between early onset (i.e., type II-younger than age 25) and late onset (i.e., type Iolder than age 25) alcoholism. When a drug that mimics certain effects of the neurotransmitter serotonin, called mchlorophenylpiperazine (mCPP), was given to detoxified alcoholics, it led to alcohol craving in many early onset alco holics but to heightened anxiety, a very different effect, in late onset alcoholics. This outcome implies that a physiological difference in certain serotonin functions exists between the two types of alcoholics. A possible difference in serotonergic function in the two groups also is suggest ed by the fact that early onset alcoholics also have relatively lower levels of sero tonin activity in the brain. Early onset alcoholics may have normal levels of serotonin while drinking, although many of them have abnormally low levels when abstinent. Results from similar challenge paradigms suggest that numerous biologi cal differences may exist between alco holics and nonalcoholics. Thus, in some patients, drinking may represent a form of selfmedication, in which alcohol is used to raise inherently low levels of serotonin or other important chemicals.
Pharmacologicalchallenge research also has demonstrated that the brain un dergoes significant adaptive changes as a result of longterm, excessive alcohol consumption. Administration of sodium lactate causes panic in individuals who have panic disorder. But when it is given to detoxified alcoholics diagnosed as having panic disorder, it results in a lower frequency of panic attacks than it does in nonalcoholic patients with panic disorder. Such adaptive changes undoubtedly play a role in alcohol tolerance as well as determine the withdrawal symptoms that ensue when drinking is stopped.

Techniques for Prevention
The IRP's ultimate objective is not only to understand the mechanisms governing alcohol's effects but also to employ this knowledge for better prevention and treatment of alcohol abuse's effects. For example, if some of alcohol's deleterious effects, such as those on the liver and nervous system, are related to reduced levels of polyunsaturated fatty acids (as discussed earlier), simple strategies for preventing or treating these complications may be to avert these losses or to restore the proper levels. Modern nutritional research already has described diets to accomplish these ends for both the liver and the peripheral nervous system. Some success has been achieved in preventing the alcoholinduced losses in liver lipids during continuous alcohol exposure. The brain is more refractory to dietary manip ulation, and in fact, alcohol is one of the few biochemical or nutritional means of altering neural fatty acid levels. It is still unknown whether the strategy of altering diet can be applied successfully to prevent some of the neuropathological and central nervous system functional deficits caused by alcohol. If such diets were even par tially successful, they would represent a simple and inexpensive way to help pre vent some of alcohol's damaging effects on both adult alcoholics and their children (e.g., alcoholrelated birth defects).

Medications That Assist in Treatment
The use of medications to assist alco holics in remaining abstinent has a long history. Disulfiram, better known by the trade name Antabuse ® , is probably the most widely used drug for this purpose. However, it is somewhat effective only in alcoholics who are highly motivated to avoid drinking, and it may cause serious side effects. Should alcohol be deliberate ly or inadvertently consumed after ingest ing disulfiram, the body's reactions range from acutely unpleasant flushing and nausea to lifethreatening responses, depending on the amount ingested and the individual's sensitivity to the drug's effects. The IRP's continuing goal is to search for medications that can specifical ly block alcohol's effects, reduce its reinforcing properties, or otherwise alter the impulse to drink without having seri ously toxic effects.

FUTURE DIRECTIONS
If earlier research productivity is any indication, the IRP's future is likely to be as impressive as its past. In some areas, intramural scientists have pioneered impor tant research, including the role of NMDA neurotransmitter receptors in alcohol intoxication and dependence and more recently the role of other receptors (e.g., 5hydroxytryptamine3 [5HT3] and adenosine triphosphate) in the brain in producing alcohol's effects. For example, the IRP is one of the few alcohol research programs in the world fully capable of exploiting new molecular neurobiological advances in receptor research.

Polymorphic Gene Research
Certain PET imaging studies are important to the further exploration of the brain function of polymorphic genes (i.e., genes with multiple forms that vary among indi viduals) that are thought to be involved in alcoholism susceptibility. These PET studies employ chemical compounds (which are injected) that are capable of tagging proteins encoded by the genes so that the proteins appear lit up on the image. Another important step in polymorphic gene research involves determining the consequences to a person's physiological and behavioral functioning of expressing certain gene forms as proteins.
The IRP also is pursuing the technical objective of inserting polymorphic genes into expression systems, such as frog eggs, to investigate the genes' molecular and cellular physiology. This work is essential in determining which genes are associated with alcoholism; how varia tions in those genes, or their expression, produce susceptibility; and how cellular functions are changed by the products that result from gene variability.

Animal Models Research
In the animal research area, investigators are planning studies of transgenic ani mals, which carry human deoxyribonucle ic acid (DNA). This will allow detailed studies of human genetics in an animal model. Similarly, selectively breeding monkeys for their vulnerability to alcohol abuse and for poor control of behavioral impulsiveness may provide researchers with a useful animal model of human alcoholic behavior.

CONCLUSIONS
As in other health areas, basic alcohol research is likely to yield significant benefits that are difficult to predict in advance. If the history of science demon strates anything, it is that research on the basic mechanisms underlying outcomes is more likely to produce important breakthroughs than is more narrowly defined applied research. Both types of research, however, clearly are needed because they complement each other. The continuing task of NIAAA's intra mural scientists is to pursue research of the highest quality in both basic and applied areas and to provide leadership in alcohol research in ways that only such a diverse program with a critical mass of expertise can. ■

ALCOHOL AND TOLERANCE
The current issue of the National Institute on Alcohol Abuse and Alcoholism's Alcohol Alert series examines how tolerance develops, how it influences drinking behavior, and its implications for alcoholism treatment.